EP1878321B1 - Control device for a discharge lamp - Google Patents

Control device for a discharge lamp Download PDF

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Publication number
EP1878321B1
EP1878321B1 EP05750124A EP05750124A EP1878321B1 EP 1878321 B1 EP1878321 B1 EP 1878321B1 EP 05750124 A EP05750124 A EP 05750124A EP 05750124 A EP05750124 A EP 05750124A EP 1878321 B1 EP1878321 B1 EP 1878321B1
Authority
EP
European Patent Office
Prior art keywords
voltage
val
vdct1
lamp
input
Prior art date
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Active
Application number
EP05750124A
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German (de)
English (en)
French (fr)
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EP1878321A1 (en
Inventor
Luca Giussani
Luca Salati
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
STMicroelectronics SRL
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STMicroelectronics SRL
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Publication date
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Publication of EP1878321A1 publication Critical patent/EP1878321A1/en
Application granted granted Critical
Publication of EP1878321B1 publication Critical patent/EP1878321B1/en
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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
    • H05B41/295—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices and specially adapted for lamps with preheating electrodes, e.g. for fluorescent lamps
    • H05B41/298—Arrangements for protecting lamps or circuits against abnormal operating conditions
    • H05B41/2981—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the circuit against abnormal operating conditions
    • H05B41/2983—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the circuit against abnormal operating conditions against abnormal power supply conditions

Definitions

  • the present invention refers to a device for driving discharge lamps, in particular fluorescent lamps.
  • Fluorescent lamps are typically composed of a glass tube which contains a small quantity of mercury, a low pressure inert gas and phosphorous powders which coat the inside part of the tube. At the extremities two electrodes are present which, connected to a suitable driving circuit, create the arc that permits the discharge of the gas to be generated and maintained.
  • ballast circuits are circuits at whose output an alternating voltage signal is generated at a frequency and amplitude necessary to keep the lamp on; this waveform is produced by a circuit that comprises a couple of transistors that switch at a frequency of tens of KHz, a current limiting coil and a filtering capacitance.
  • ballast circuits must detect this failure condition, when it exceeds a certain level, and undertake suitable preventive measures such as turning off the ballast.
  • ballast circuit for a discharge lamp 10 having two cathodes ( Figure 1 ) in which the ballast circuit comprises an inverter 1, driven by a device 11, that provides for an alternated voltage at its output terminals; the inverter 1 is fed through a voltage Val coming from a PFC or from a rectification stage 100 fed in turn by the mains voltage Vin.
  • the ballast comprises a circuitry 2 to couple the discharge lamp 10 to said output terminals, another circuitry 3 that measures a direct voltage component Vdc1 at the ends of the blocking capacitor C1 placed between the lamp and ground GND and means 4 suitable for deactivating the inverter 1 when the lamp approaches the ageing conditions.
  • the measured direct component Vdc1 is compared with a signal Vdcm referred to ground GND and produced by means 5; when said component Vdc1 is less or greater than the signal Vdcm by a given value, the means 4 turn off the inverter 1 by acting on the device 11 through a signal Dis.
  • the proposed solution does not consider a problem linked mainly to the variations of the input voltage of the inverter, whether it be the mains voltage rectified or the output of a stage of the power factor correction (PFC). These variations can be due to low values of the input capacity of the inverter, to short interruptions of the mains voltage that cause a voltage drop or to transitory phenomena that cause its variation.
  • an oscillation at a frequency equal to twice the mains voltage frequency is overlaid to the direct value of the input voltage of the inverter; the amplitude of this oscillation is inversely proportional to the value of the capacity (electrolytic) placed downstream of the rectifier stage (normally a diode bridge) or of the PFC.
  • circuitry proposed in the abovementioned patent also intervenes in presence of one of the abovementioned variations of the inverter input voltage, even though the lamp does not present any type of ageing condition.
  • US patent 6,288,500 B1 discloses a circuit arrangement which also detecs the lamp's ageing conditions.
  • the object of the present invention is to provide a device for driving discharge lamps that overcomes the abovementioned inconvenience.
  • this object is achieved by means of a control device for a discharge lamp as defined in claim 1.
  • the present invention it is possible to produce a driving device for a discharge lamp that prevents the substitution of the discharge lamp in presence of variations of the supply voltage of the same driving device.
  • the driving device of Figure 2 preferably a ballast circuit, provides for driving a fluorescent lamp 10 having two cathodes.
  • the ballast circuit comprises an inverter 1, driven by a device 11, that provides for an alternating voltage on its output terminals; the inverter 1 is fed by a voltage Val coming from a device for the power factor correction (PFC) or from a rectification stage 100 fed in turn by the mains voltage Vin.
  • PFC power factor correction
  • the ballast circuit comprises a circuitry 2 to couple the fluorescent lamp 10 to said output terminals, another circuitry 3 that measures a direct voltage component Vdc at the ends of the blocking capacitor C1 placed between the lamp and ground GND and means 40 suitable for deactivating the inverter 1 when the lamp approaches the ageing ("end of life") conditions, that is when a depletion of the emissive coating of one of the cathodes of the same lamp occurs, so as to prevent excessive heating of said cathode.
  • the driving circuit comprises means 50 suitable for supplying a direct voltage component Vdca depending on said supply voltage Val, more precisely aligned or proportional in value to said supply voltage Val.
  • the measured direct component Vdc is compared with the signal Vdca; when said component Vdc is lower or higher than the signal Vdca by a given value D the means 40 provide for turning off the inverter 1 by acting on the device 11 through a signal Dis.
  • Said given value D is, for example, within a field of variation between 2 and 52 volts.
  • the means 50 comprise a device capable of supplying a voltage signal proportional to the voltage Val, preferably a resistive divider comprising two resistors R51 and R52 arranged in series between the supply voltage Val and ground GND.
  • the common terminal of the two resistors R51 and R52 is the input terminal of a buffer 51 and on said terminal there is the signal Vr; the output terminal of the buffer 51 is the common terminal of two resistors R1 and R2 having the other terminals connected respectively to two current generators I1 and I2 in turn connected respectively to a supply voltage Vdd and to ground GND.
  • the threshold voltages Vdct1 and Vdct2 are taken respectively on the common terminal of the resistor R1 and of the current generator I1 and on the common terminal of the resistor R2 and of the current generator 12; said voltages Vdct1 and Vdct2 are in input to the means 40.
  • the latter comprise a comparator having in input the voltages Vdct1, Vdct2 and Vdc.
  • the threshold voltages Vdct1 and Vdct2 represent the reference voltage Vdca of the means 40 that depends on the supply voltage Val; in fact the voltages Vdct1 and Vdct2 depend on the voltage Vr that varies in accordance with a variation of the voltage Val.
  • FIG 4 an even more detailed circuit diagram of a part of the device of Figures 2 and 3 is shown.
  • the circuitry 3 comprises a series of two resistors R31, R32 placed at the ends of the capacitor C1; the signal detected on the common terminal of the two resistors R31, R32 is the signal Vdc that is in input to the means 40, more precisely in input to the comparator.
  • the means 50 comprise a resistive divider comprising two resistors R51 and R52 arranged in series between the supply voltage Val and ground GND.
  • the common terminal of the two resistors R51 and R52 is the inverting input terminal of an operational amplifier 52 and on said terminal there is the signal Vr; the output terminal of the operational amplifier 52 is the gate terminal of the transistor M1 having the source terminal connected to ground GND and the drain terminal connected to a terminal of a resistor R2.
  • the latter has its other terminal connected to the non-inverting terminal of the operational amplifier 52 and to the resistor R1 having its other terminal connected to a current generator I1; preferably said current generator I1 is controlled by a circuit bandgap 53 to obtain a precise current reference.
  • the threshold voltages Vdct1 and Vdct2 are taken respectively at the common terminals of the resistor R1 and of the current generator I1 and of the resistor R2 and of the transistor M1 and are in input to the comparator of the means 40.
  • the threshold voltages Vdct1 and Vdct2 represent the reference voltage Vdca of the means 40 that depends on the supply voltage Val; in fact the voltages Vdct1 and Vdct2 depend on the voltage Vr that varies in accordance with a variation of the voltage Val.
  • FIG 5 a time diagram of signals in question in the circuit of Figure 1 according to the known art is shown.
  • a variation of the supply voltage Val causes a similar variation of the voltage Vdc1.
  • the reference signal Vdcm is constituted by two fixed threshold voltages, a threshold voltage exceeding Vt2 and a threshold voltage lower than Vt1
  • the variation of the voltage Vdcm causes a lowering of the same voltage Vdc1 below the threshold voltage Vt1
  • the ballast circuit according to the known art operates in an incorrect manner given that it turns off the fluorescent lamp 10 not in presence of an ageing condition of the same but in presence of a variation of the supply voltage Val.
  • a variation of the supply voltage Val causes a similar variation of the voltage Vdc but not the sending of the signal Dis to the circuitry 11.
  • the variation of the voltage Val also causes a similar variation of the threshold voltages Vdct1 and Vdct2, so that the voltage Vdc does not go lower than the threshold voltage Vdct1
  • the signal Dis remains therefore a nil signal.
  • the driving circuit according to the invention operates correctly given that it does not turn off the fluorescent lamp 10 in presence of a variation of the supply voltage Val.

Landscapes

  • Circuit Arrangements For Discharge Lamps (AREA)
EP05750124A 2005-05-04 2005-05-04 Control device for a discharge lamp Active EP1878321B1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/IT2005/000258 WO2006117809A1 (en) 2005-05-04 2005-05-04 Control device for a discharge lamp

Publications (2)

Publication Number Publication Date
EP1878321A1 EP1878321A1 (en) 2008-01-16
EP1878321B1 true EP1878321B1 (en) 2010-04-07

Family

ID=35106711

Family Applications (1)

Application Number Title Priority Date Filing Date
EP05750124A Active EP1878321B1 (en) 2005-05-04 2005-05-04 Control device for a discharge lamp

Country Status (5)

Country Link
US (1) US7902764B2 (es)
EP (1) EP1878321B1 (es)
CN (1) CN101171888B (es)
DE (1) DE602005020520D1 (es)
WO (1) WO2006117809A1 (es)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE502007006528D1 (de) * 2007-03-29 2011-03-31 Osram Gmbh Schaltungsanordnung zur ansteuerung mindestens einer leuchtstofflampe
DE102009004851A1 (de) * 2009-01-16 2010-07-29 Osram Gesellschaft mit beschränkter Haftung Detektorschaltung und Verfahren zur Ansteuerung einer Leuchtstofflampe
DE102009004852A1 (de) * 2009-01-16 2010-07-29 Osram Gesellschaft mit beschränkter Haftung Detektorschaltung und Verfahren zur Ansteuerung einer Leuchtstofflampe
CO6530147A1 (es) * 2011-09-23 2012-09-28 Panacea Quantum Leap Technology Llc Balaso electrónico
MX2016001416A (es) * 2013-07-30 2016-08-18 Gen Electric Circuito de proteccion de termino de vida de lampara t5.

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06215886A (ja) * 1993-01-14 1994-08-05 Matsushita Electric Works Ltd 電源装置
US5475284A (en) * 1994-05-03 1995-12-12 Osram Sylvania Inc. Ballast containing circuit for measuring increase in DC voltage component
US5883473A (en) * 1997-12-03 1999-03-16 Motorola Inc. Electronic Ballast with inverter protection circuit
DE19837728A1 (de) * 1998-08-20 2000-02-24 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Schaltungsanordnung zum Betrieb mindestens einer Entladungslampe
US5969482A (en) * 1998-11-30 1999-10-19 Philips Electronics North America Corporation Circuit arrangement for operating a discharge lamp including real power sensing using a single quadrant multiplier
US6362575B1 (en) * 2000-11-16 2002-03-26 Philips Electronics North America Corporation Voltage regulated electronic ballast for multiple discharge lamps
CN1582605A (zh) * 2001-11-07 2005-02-16 皇家飞利浦电子股份有限公司 具有灯使用期限检测的放电灯镇流器电路安排
DE10163033A1 (de) 2001-12-20 2003-07-03 Tridonicatco Gmbh & Co Kg Elektronisches Vorschaltgerät mit Überwachungsschaltung zum Erkennen des in einer Gasentladungslampe auftretenden Gleichrichteffekts

Also Published As

Publication number Publication date
CN101171888B (zh) 2011-01-05
CN101171888A (zh) 2008-04-30
US20090121639A1 (en) 2009-05-14
DE602005020520D1 (es) 2010-05-20
WO2006117809A1 (en) 2006-11-09
US7902764B2 (en) 2011-03-08
EP1878321A1 (en) 2008-01-16

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